1. Field of the Invention
The invention relates generally to wireless communication and more particularly to systems and methods for antennas with multiple ground plane sections.
2. Background
Consumers are increasingly demanding smaller and smaller feature rich wireless communication devices, such as, for example, cellular telephones (hereinafter “cell phones”). One way to achieve a smaller cell phone with more functions and features is to produce a cell phone with two configurable housing portions. One such configuration is a flip phone. A flip phone opens up like a clam shell. Other such configurations are sliding phones and swivel phones. In a sliding phone, one portion of the cell phone housing slides relative to the other portion. In a swivel phone, one portion of the cell phone swivels open, relative to the other portion. A sliding phone is shown with respect to U.S. patent application Ser. No. 10/931,712, filed on Sep. 1, 2004, attorney docket number UTL 00372, the whole of which is hereby incorporated herein by reference.
Typically one configuration of the two housing portions is smaller than the other configuration. Typically, the smaller configuration is called the closed configuration and the larger configuration is called the open configuration. The cell phone user can keep the cell phone in the closed configuration when carrying the cell phone, or for storage. Then the cell phone can be put in the open configuration to be used. Some phones can be used in both configurations.
In some configurable cell phones, both housing portions have a ground plane. Ground planes effect the performance of any nearby (proximate) antenna. Specifically, an antenna might perform optimally with the cell phone in one configuration, but sub-optimally with the cell phone in the other configuration. The sub-optimal performance could be due to the positional change of one of the ground planes relative to the antenna. Especially, an antenna that depends heavily on the ground plane, such as a patch antenna or a planar inverted F antenna (PIFA), may perform poorly when a grounded metal is near the antenna in some configurations.